The iconic piano from the film Casablanca is to go up for auction in New York.

Character Sam (Dooley Wilson) sings As Time Goes By on the 58-key instrument in a romantic flashback scene between Rick (Humphrey Bogart) and Isla (Ingrid Bergman).

The piano will be sold at Sotheby's on December 14 to coincide with the 70th anniversary of the film.

David Redden, Sotheby's vice chairman, estimates the piano to fetch anywhere between $800,000 and $1.2m.

He said: "I think Hollywood memorabilia has become more and more significant as time's gone on, as time goes by.

Image Caption:Sam famously singing As Time Goes By

"In fact back in 1988 this was an extraordinary object but it's grown in stature because the movie has become ever more iconic as the years go by. And this really is the symbol of the movie. It's one of the greatest romantic movie props of all time."

The piano is a surprising green and yellow in colour and compact in size.

Mr Redden said: "Seeing the piano like this is a bit of a revelation because in the movie it's in black and white. And here we are, we see green and yellow and all sorts of things. But it's as it appeared in the movie, except just now in living colour.

"It would've been made as a small, what they call studio piano which could be wheeled from table to table in a cafe, which is why it's small as it is. Very compact, made in Los Angeles, probably in the late 1930s."

The piano was first auctioned by Sotheby's in 1988 to a Japanese collector. According to Sotheby's, at that time the price paid was one of the highest ever achieved for a movie prop.